A previously proposed blowing lance is formed of a metal tube surrounded by a sheath of refractory material over at least part of its length. In a lance intended for blowing oxygen, the tube is made of copper; in a lance intended for blowing an inert gas, the tube is made of steel. At present there is no lance which can be used both for blowing oxygen and for blowing an inert gas, so that, in steel works, it is at present necessary to have available the two types of lance. The first type of lance in effect serves to heat up the steel in the ladle to bring the temperature of the liquid steel to the value strictly set for casting. A lance of the second type is used for homogenising the steel in the ladle. Furthermore, in general, the known lances only comprise a single tube.